Stabilized oiled coal slurry in water



No Drawing. Filed May 22, 1962, Ser. No. 196,611 2 Claims. (Cl. 44'-51) This invention relates to a stabilized slurry of pulverized coal coated with a liquid hydrocarbon fuel in water to make the slurry suitable for pumping through a pipeline. In particular, this invention is concerned with stabilizing the pulverized coal coated with hydrocarbon oil using an imidazoline surfactant which stabilizes the dispersion of the oil-coated pulverized coal in a relatively small amount of water.

Tests have been carried out to demonstrate that an aqueous coal slurry containing at least 30 to 40 wt. percent water can be pumped through pipelines for transportation to where the coal is to be burned. However, there are disadvantages in using only water as the liquid medium in that the water of such proportions, above 20%, makes combustion of the slurry in the furnace less eflicient. Difliculties also arise in the transporting of an aqueous slurry or oil slurry of coal in the tendency of the powdered coal to settle out.

The present invention has been found to provide a more suitably powdered coal slurry in a composition with petroleum oil and a more limited amount of water, particularly when the mixture is stabilized by the use of a relatively small amount of imidazoline which serves to stabilize the slurry.

The imidazoline agent has the general formula:

wherein R is an aliphatic hydrocarbon chain radical containing 10 to 23 carbon atoms. The aliphatic radical may be an alkyl group such as present in high molecular weight fatty acids, e.g., lauric, myristic, palmitic, stearic, archidic and carnaubic. The aliphatic radical may be alkenyl radical or an alkdienyl radical, or in other words, an unsaturated aliphatic radical such as present in the following unsaturated acids, e.g., oleic, linoleic, linolinic and eurcic.

These imidazolines and methods for their preparation are described in U.S. Patent 2,361,488 of Louis A. Mikeska.

The stable coal slurry compositions made in accordance with the present invention using pulverized coal coated with hydrocarbon oil dispersed in water should contain about 15 to 20 Wt. percent of water. Larger amounts than this proportion give unsatisfactory combustion and difliculties in maintaining a stable slurry. The proportion of hydrocarbon oil, e.g., crude petroleum oil or a petroleum fuel oil, used in coating the coal particles is in the range of about 25 to 35 wt. percent. The amount of pulverized coal used in the slurry is in the range of 45 to 55 wt. percent. The amount of the surfactant agent in the slurry formulation is about 0.3 to 2 wt. percent. The pulverized coal is preferably of a particle size to make substantially all the pulverized coal pass through an 8 mesh sieve, and with about 90% which would be retained on a 200 mesh sieve. In these slurries, the hydrocarbon oil, with the aid of the imidazoline surfactant in small amount, coats the coal particles and replaces the amount of water that cannot be tolerated for stable suspension and satisfactory combustion.

In preparing a composition containing the maximum amount of water, 20 wt. percent water, the pulverized United States Patent dered coal suspension to obtain the following slurry formulation:

Percent Pulverized coal 50.0 Water 20.0 Fuel oil 28.0 Imidazoline surfactant 2.0

Petroleum fuel oils found suitable for use in the formulations are residual oils of the following types:

Inspection of heavy fuel oils from various crudes Venezuelan U.S.A.

Middle East 1 2 East West Coast Coast Specific Gravity 60 FL... 0.962 0.980 1.008 0.971 0.983 Closed Flash Point, F. 192 162 210 180 200 Viseoslty Redwood, Sec.

F 3, 570 3, 745 4, 050 1, 850 3, 347 Sulfur Content, percent..... 2. 17 2. 65 l. 7 1. 24 4. 5 Gross Oalorifie Value,

B.t.u./lb 18, 540 18, 440 18,200 18, 490 18, 290

In general, the more suitable residual fuel oils for use in the slurries have specific gravities of about 0.9 to 1 (at 60 F.) and viscosities about 40 to 300 Saybolt furol seconds at 122 F.

The pulverized coal may be of various types of coal, e.g. bituminous, anthracite, or semi-bituminous. Other finely-divided solid carbonaceous materials may be used, e.g. coke either from coal or petroleum.

The following example describes a slurry formulation which was considered closer to the optimum in stability.

Slurry formulation 1 Residual type oils for burner installation equipped with preheating facilities.

This slurry formulation showed no appreciable tendency to settle out after standing for over 24 hours. It has suitable fluidity under pressure for pumping through a pipeline, being equivalent in this respect to a slurry of 60 wt. percent pulverized coal in 40 wt. percent water.

The invention described is claimed as follows:

1. A stabilized aqueous slurry of powdered coal and residual petroleum fuel oil which comprises 8 to 200 mesh particle coal in a proportion of 45 to 50 wt. percent, 25 to 35 wt. percent of petroleum residual oil having a 3 4- specific gravity of 0.9 to 1 at 60 F. and a Saybolt furol viscosity of 40 to 300 seconds at 122 F., 15 to 20 wt. 1% E percent water and about 0.3 to 2.0 wt. percent of an imidazoline surfactant of the formula:

Hg-CHr-NH;

wherein R represents a C to C aliphatic hydrocarbon NCH1 radical, the powdered coal being coated by the hydro- R(".|; 43H, carbon oil containing the imidazoline and the thus-coated powdered coal being suspended in the water. N 10 I 1 References Cited by the Examiner UNITED STATES PATENTS wherein R represents heptadecenyl and heptadecadienyl g &2; chains, the powdered coal being coated with the oil con- 2622018 12/52 32 44 63 taining the surfactant. i 1 e e a 2. A stabilized aqueous slurry of powdered coal and FOREIGN PATENTS oil which comprises about 45 to 50 wt. percent of pow- 408 951 4/34 Great Britain dered coal, about to wt. percent of hydrocarbon 454:796 10/36 Great Britain fuel oil, 15 to 20 wt. percent water, and about 0.3 to 2.0 wt. percent of an irnidazoline having the formula:

DANIEL E. WYMAN, Primary Examiner. 

1. A STABILIZED AQUEOUS SLURRY OF POWDERED COAL AND RESIDUAL PETROLEUM FUEL OIL WHICH COMPRISES 8 TO 200 MESH PARTICLES COAL IN A PROPORTION OF 45 TO 50 WT. PERCENT, 25 TO 35 WT. PERCENT OF PETROLEUM RESIDUAL OIL HAVING A SPECIFIC GRAVITY OF 0.9 TO 1 AT 60*F. AND A SAYBOLT FUROL VISCOSITY OF 40 TO 300 SECONDS AT 122*F., TO 20 WT. PERCENT WATER AND ABOUT 0.3 TO 2.0 WT. PERCENT OF AN IMIDAZOLINE SURFACTANT OF THE FORMULA: 